The present invention relates generally to light guides for radiation detectors, and more particularly to methods of manufacturing, and articles of manufacture produced thereby, for light guides for radiation detectors used in medical or other imaging.
FIG. 1 shows a conventional scintillator-based radiation detector, such as may be used in positron emission tomography (PET). The detector 2 comprises a set of scintillator crystals 4 optically coupled to respective photomultiplier tubes (PMTs) or other types of photosensors, for example, photodiodes, avalanche photodiodes (APDs), Geiger mode APDs, silicon photomultipliers (SiPMs), electron multiplying charge coupled devices (EMCCDs), pin diodes, etc. 8 via individual light guides 6. The scintillators 4 may be made of suitable crystals such as bismuth germanate (BGO), lutetium oxyorthosilicate (LSO), barium fluoride (BaF2) or the like which emit visible, ultraviolet or other detectable light when struck with high-energy gamma photons, such as the 511 keV coincidence photons detected in PET diagnostic imaging. As shown in FIG. 1, when a gamma photon is emitted from point 10 (e.g., from within the body of a patient who has been injected with a positron- or gamma-emitting radiopharmaceutical), the photon may strike and be stopped (absorbed) by the scintillator 4 at point 12, which causes detectable light to be emitted (i.e., the scintillator will “scintillate”). The light guide 6, which may be made of optical glass, plastic or other suitable material, conveys the detectable light to its respective photosensor 8. The photosensors collect these scintillation “counts” over time, which the PET system uses to later construct images showing the distribution and concentration of radiopharmaceutical throughout the patient's body.
As illustrated in FIG. 2, individual light guides 6 are typically frustum-shaped (i.e., like a cone or pyramid truncated by a plane that is parallel to the cone/pyramid base). (Note that the light guides shown in FIG. 2 are oriented upside-down from the orientation illustrated in FIG. 1.) This frustum shape accommodates the size and shape of the scintillators 4 which abut one surface 32 of the light guide 6, as well as the typically smaller size and shape of the photosensors 8 which abut the opposite surface 28. One difficulty experienced with assembling PET or other scintillation detectors is handling and mounting the large number of individual light guides 6. For example, in a single 3×4 detector module, twelve individual light guides must be handled and mounted; multiplying this by the typically large number of modules used in a PET system, it becomes clear how challenging it is to handle and mount such a large number of individual light guides. Added to this, there is the additional challenge of making sure all the individual light guides are aligned properly and consistently. Furthermore, with the repeated handling of numerous individual light guides, there is increased likelihood that the human assemblers may damage or misalign the light guides, thus potentially compromising scintillation count rates, consistency and image quality.
It would be desirable, therefore, to provide an improved way of manufacturing and assembling light guides for PET/radiation detectors which avoids or minimizes the drawbacks mentioned above.